COMPLEMENTARY ANGLES: Two angles whose sum is 90˚

SUPPLEMENTARY ANGLES: Two angles whose sum is 180˚

How to keep that straight?◦ The alphabet! (complementary comes before

supplementary; 90 comes before 180)◦ Complements are nice, but supplements complete

you (make a straight line)

Example: Name a pair of adjacent complementary angles.◦

Name a pair of nonadjacent complementary angles◦

STV and VTR

PTQ and VTR

Example: Name a pair of nonadjacent supplementary angles.◦

Find the measure of an anglethat is supplementary toCFD◦

BFC and AFE

180 – 45 = 135˚

Angles A and B are complementary. If mA = x and mB = 5x, find x. Then find mA and mB.◦ Because these are complementary angles, they

add together to equal 90˚.◦ x + 5x = 90◦ 6x = 90 (combine like terms)◦ x = 15 (divide by 6)

To find mA and mB, simply substitute x back in.◦mA = 15˚◦mB = 5(15) = 75˚

Postulate 3-4: If two angles form a linear pair, they are supplementary.

If m1 = 57 and 1 and 2 form a linear pair, find m2.◦ 180 – 57 = 123˚

Assignment◦ Worksheet #3-5